The objective of this research program is to develop a miniaturized Surface Acoustic Wave (SAW) 4 Sensor Array Vapor Detection System for use as a personal monitor for toxic gases. The SAW sensors are the most promising of a number of chemically sensitive microelectronic devices that have received considerable attention recently because they can be made by planar microfabrication techniques. Because of their basic solid state construction and compatibility with integrated electronics, they will have many advantages over currently available toxic vapor detectors which are based on other technologies. The microelectronic devices have the potential to be very small, rugged, sensitive, easily manufactured, and low cost on a large volume basis. They have been successfully demonstrated in several prototype configurations, but no significant effort has yet been made to reduce their size and weight to the extent possible with current state-of-the-art electronic technology. Until these solid state vapor sensors and associated components are successfully miniaturized, their full potential, include cost savings, will not be realized. Successful completion of this research effort could make possible a new class of toxic vapor monitors that have many advantages over those now available.